Recently, a thermoelectric power-generating technology for which the system is simple and can be down-sized has been specifically noted as a power recovery technology for unharnessed exhaust heat energy that is generated from fossil fuel resources and others used in buildings, factories, etc. However, thermoelectric power generation is, in general, poorly efficient in power generation, and therefore, studies and developments are being actively made for improving power generation efficiency in various companies and research institutes. For improving power generation efficiency, it is indispensable to enhance the efficiency of thermoelectric conversion materials, and for realizing it, it is desired to develop materials having a high electrical conductivity comparable to that of metals and having a low thermal conductivity comparable to that of glass.
A thermoelectric conversion characteristic can be evaluated by a figure of merit Z (Z=σS2/λ). Here, S means a Seebeck coefficient, σ means an electrical conductivity (reciprocal of resistivity), and λ means a thermal conductivity. Increasing the value of the figure of merit Z improves the power generation efficiency, and for enhancing the efficiency in power generation, it is important to find out a thermoelectric conversion material having a large Seebeck coefficient and a large electrical conductivity σ, and having a small thermal conductivity λ.
As described above, investigations for improving power generation efficiency are needed while, on the other hand, thermoelectric conversion devices that are now produced are poor in mass-productivity and the power generation units therein are expensive. Consequently, for further disseminating the devices in use in large areas, for example, in installation thereof on the wall surface of buildings, production cost reduction is imperative. In addition, thermoelectric conversion devices that are produced at present are poorly flexible, and therefore flexible thermoelectric conversion devices are desired.
Given the situation, PTL 1 discloses, for the purpose of improving power generation efficiency and for efficient production, a method for producing a thermoelectric conversion device that comprises a step of applying a solution to be a material of a p-type or n-type organic semiconductor material, onto a support having patterned insulator layer to the surface thereof by coating or printing thereon followed by drying it. However, the method requires patterning that includes alignments to be repeated plural times, such as screen printing or the like, and therefore the step is complicated and, as a result, the takt time is long, therefore providing a problem of rising costs.
On the other hand, in NPL 1, an investigation is made, using a composition prepared by dispersing, as a thermoelectric conversion material, bismuth telluride in an epoxy resin as a binder, and forming the composition into a film by coating, thereby producing a thin-film thermoelectric conversion device. However, this requires a sintering process at a high temperature not lower than the decomposition temperature of the binder resin, and therefore still has a problem in that the flexibility of the produced film could be on the same level as that in the case of forming a film of bismuth telluride alone.